Toner systems employed in connection with an imaging apparatus typically fall into two classes: (1) two-component development (TCD) systems, in which the developer materials include magnetic carrier granules and toner particles designed to triboelectrically adhere to the carrier; and (2) single-component development (SCD) systems, which rely on toner particles without the presence of a carrier which are charged relative to a charging blade.
The charging requirements for toners in SCD systems are very different from those employed in TCD systems. A particular challenge in SCD systems is achieving adequate charging under high temperature and high humidity environments, such as those designated as “A-zone,” about 28° C./85% relative humidity. In order to achieve sufficient triboelectric charge, a charge control agent (CCA) is typically associated with the toner particle.
One means to add a CCA to toner particles is by dry blending the CCA as a surface additive. By way of example, a CCA may be dry blended onto styrene/acrylate emulsion aggregation (EA) toner particles. In use, it has been observed that such surface-modified EA toner particles suffer from drop-off in density after about 10,000 prints.
A second option to associate a CCA with toner particles is to add the CCA at the polymer synthesis stage. For example, in an EA system such as that described above, the CCA may be added to an emulsion of monomers and an emulsion polymerization carried out. The resultant product comprises EA toner particles with CCA incorporated into the polymer matrix. In general, such CCA-doped EA toner particles may perform better than their dry-blended surface-modified counterparts. However, the process for performing the emulsion polymerization in the presence of a CCA is not always reproducible and/or scale up is not always readily achieved. In numerous instances, problems may arise with reactor fouling.